The lifetime and power output of alternators depends, to some extent, on the efficiency and operation of the bearings journalling the rotor of the alternator. It is preferred to provide oil lubrication for rolling-type bearings, and in some applications it is desirable to provide pressure lubrication for the bearings. Pressurized lubricant can be obtained by connecting the pressure lubrication circuit of the alternator to the oil pressure circuit of a motor vehicle of which the alternator is a part. It is, of course, also possible to provide a separate pressurized oil supply source for the alternator.